6 Search Results

We present non-perturbative lattice calculations of the low-lying meson and baryon spectrum of the SU(4) gauge theory with fundamental fermion constituents. This theory is one instance of stealth dark matter, a class of strongly coupled theories, where the lowest mass stable baryon is the dark matter candidate. This work constitutes the first milestone in the program to study stealth dark matter self-interactions. Here, we focus on reducing excited state contamination in the single baryon channel by applying the Laplacian Heaviside method, as well as projecting our baryon operators onto the irreducible representations of the octahedral group. We compare our resultingmore » spectrum to previous work involving Gaussian smeared non-projected operators and find good agreement with reduced statistical uncertainties. We also present the spectrum of the low-lying odd-parity baryons for the first time.« less

In the large- N and strong-coupling limit, maximally supersymmetric SU (N) Yang-Mills theory in (2 + 1) dimensions is conjectured to be dual to the decoupling limit of a stack of N D2-branes, which may be described by IIA supergravity. We study this conjecture in the Euclidean setting using nonperturbative lattice gauge theory calculations. Our supersymmetric lattice construction naturally puts the theory on a skewed Euclidean 3-torus. Taking one cycle to have antiperiodic fermion boundary conditions, the large-torus limit is described by certain Euclidean black holes. We compute the bosonic action—the variation of the partition function—and compare our numerical resultsmore » to the supergravity prediction as the size of the torus is changed, keeping its shape fixed. Our lattice calculations primarily utilize with extrapolations to the continuum limit, and our results are consistent with the expected gravity behavior in the appropriate large-torus limit.« less

We use non-perturbative lattice calculations to investigate the finite-temperature confinement transition of stealth dark matter, focusing on the regime in which this early-universe transition is first order and would generate a stochastic background of gravitational waves. Stealth dark matter extends the standard model with a new strongly coupled SU(4) gauge sector with four massive fermions in the fundamental representation, producing a stable spin-0 -dark baryon- as a viable composite dark matter candidate. Future searches for stochastic gravitational waves will provide a new way to discover or constrain stealth dark matter, in addition to previously investigated direct-detection and collider experiments. Asmore » a first step to enabling this phenomenology, we determine how heavy the dark fermions need to be in order to produce a first-order stealth dark matter confinement transition.« less

Composite Higgs models must exhibit very different dynamics from quantum chromodynamics (QCD) regardless whether they describe the Higgs boson as a dilatonlike state or a pseudo-Nambu-Goldstone boson. Large separation of scales and large anomalous dimensions are frequently desired by phenomenological models. Mass-split systems are well-suited for composite Higgs models because they are governed by a conformal fixed point in the ultraviolet but are chirally broken in the infrared. In this work we use lattice field theory calculations with domain wall fermions to investigate a system with four light and six heavy flavors. We demonstrate how a nearby conformal fixed pointmore » affects the properties of the four light flavors that exhibit chiral symmetry breaking in the infrared. Specifically we describe hyperscaling of dimensionful physical quantities and determine the corresponding anomalous mass dimension. We obtain y_m = 1 + γ* = 1.47(5) suggesting that N_f = 10 lies inside the conformal window. Comparing the low energy spectrum to predictions of dilaton chiral perturbation theory, we observe excellent agreement which supports the expectation that the 4 + 6 mass-split system exhibits near-conformal dynamics with a relatively light 0⁺⁺ isosinglet scalar.« less

We smore » tudy the discrete β function of SU(3) gauge theory with N _f = 12 massless fermions in the fundamental representation. Using an nHYP-smeared staggered lattice action and an improved gradient flow running coupling ${\tilde{g}}_c^2\left(L\right)$ we determine the continuum-extrapolated discrete β function up to g _c ² ≈ 8.2. We observe an IR fixed point at g _* ² = 7.3( _-2 ^{+ 8} ) in the $c=\sqrt{8t}/L=0.25$ scheme, and g _* ² = 7.3( _-3 ^{+ 6} ) with c = 0.3, combining statistical and systematic uncertainties in quadrature. The systematic effects we investigate include the stability of the (a/L) → 0 extrapolations, the interpolation of ${\tilde{g}}_c^2\left(L\right)$ as a function of the bare coupling, the improvement of the gradient flow running coupling, and the discretization of the energy density. In an appendix we observe that the resulting systematic errors increase dramatically upon combining smaller c ≲ 0.2 with smaller L ≤ 12, leading to an IR fixed point at g _* ² = 5.9(1.9) in the c = 0.2 scheme, which resolves to g _* ² = 6.9( _-1 ^{+ 6} ) upon considering only L ≥ 16. At the IR fixed point we measure the leading irrelevant critical exponent to be γ _{g *} = 0.26(2), comparable to perturbative estimates.« less